1. Field of the Invention
This invention relates to fiber optics and more particularly to an adjustable fiber optic bulk polarizer system.
2. Description of the Prior Art
It is sometimes desirable in fiber optic systems to polarize light to be transmitted through optical fibers by the use of an optical polarizer. Prior art polarizers for optical fibers include all fiber polarizers, in which optical fibers are polished and manipulated in order to provide a polarized output of light. Such polarizers are effective but are relatively expensive and difficult to produce.
Nonfiber optic polarizing devices are called bulk polarizers. Bulk polarizers are available but are difficult to maintain in alignment with the optical fibers to maintain low optical losses. A Glan-Thompson polarizer is readily available and is effective in polarizing light, but the light must be collimated in order to achieve a high output and an acceptable ratio of polarized to non-polarized light. Bulk polarizer systems tend to be unstable because of difficulty in maintaining alignment of the component parts. The need for collimation and the need to maintain alignment has made the use of Glan-Thompson polarizers with fiber optic systems difficult.
The Glan-Thompson bulk polarizer is used in association with a fiber optic system by transmitting light from the fiber optic through graded index (GRIN) lenses. The GRIN lenses are constructed to have indices of refraction which collimate light. The GRIN lenses are contacted by the optic fibers so that light transmitted through the fiber is collimated by the GRIN lens. The bulk polarizer and two GRIN lenses are provided. A single mode polarization maintaining optic fiber carrying an input beam is connected to one GRIN lens. A single mode polarization maintaining output optic fiber is in engagement with the other GRIN lens for providing the collimated light output to the fiber optic system. Small changes in angular alignment (0.01 degrees) between the GRIN lenses produce large increases in optical losses.